Flame retardant compositions consisting essentially of a thermoplastic material and a phosphinic acid



3,322,716 FLAME RETARDANT coMrosrrroNs CONSIST- ING ESSENTIALLY MATERIAL AND A Harvey Gerald Klein and UP A THERMOPLASTIC PHGSPHINIC ACID Helen Currier Gillllam, Stamford, Conn, assignors to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Aug. 19, 1963, Ser. No. 303,156 12 Claims. (Cl. 260-453) wherein R represents an aryl radical (C -C an alkyl radical (C C or a cyano, hydroxy, carboxy, or carboxyhydroxy substituted alkyl radical, and R represents hydrogen, an aryl radical (C 10), an alkyl radical (C C or a cyano, hydroxy, carboxy or carboxyhydroxy substituted alkyl radical.

The use of various materials incorporated into thermoplastic resins in order to improve the flame retardance thereof is known in the prior art. Many compounds are commercially available for such a use, among them being chlorostyrene copolymers, chlorinated parafiln wax with triphenyl stibine, chlorinated paraflins and aliphatic antimonyl compounds, as well as antimony oxide-chlorinated hydrocarbon mixtures. A drawback, however, of these compounds and mixtures of compounds has been the fact that generally a large amount, i.e. upwards of 35% of the additive must be incorporated into the resin in order to make it sumciently flame retardant. Also these prior art additives tend to crystallize or oil out of the resin after a relatively short time of incorporation. We have now found a group of compounds which may be added to thermoplastic resins, in relatively small amounts, and still result in the production of satisfactory flame-retardant compositions which do not crystallize or oil out of the resin after incorporation therein.

The production of thermoplastic resin compositions which are flame-retardant, i.e. have high resistance to heat, is of considerable commercial importance. For example, such articles as castings, moldings, foamed or laminated structures and the like are required, or at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of such applications can be found in castings for live electrical contacts which should not be ignited or deteriorated by heat and sparks. Structural members such as pipe-s, wall coverings, wall paneling, windows, etc., and items such as ash trays, waste baskets, fibers and the like are further examples of products wherein flame retardance is desirable.

It is therefore an object of the present invention to provide novel flame retardant thermoplastic resin compositions.

It is a further object of the present invention to provide flame retardant compositions comprising thermoplastic polymers and a flame-retarding amount of a phosphinic acid, such as those represented by Formula I.

These and further objects will become more apparent to those skilled in the art upon reading the more detailed description set forth hereinbelow.

. -bromostyrenes,

3,322,7l6 Patented May 30, 1967 The thermoplastic polymers The thermoplastic polymers into which the flame retardant agents may be incorporated, either alone or in admixtures, to produce the novel compositions of the present invention, are generally the vinyl type polymers wherein the monomeric material is polymerized, by any known method, via the vinyl unsaturation therein. Additionally, thermoset type materials such as the polyester resins, polyurethanes, and the like may be used. Examples of the vinyl type polymers which may be used to form our novel compositions are the vinyl halides, the vinylidene halides, polyvinyl butyral, butadiene copolymers, acrylonitrile-butadiene-styrene polymers, the acrylonitriles, etc. Additionally and preferably, one may incorporate the flame retardant agents mentioned above into such polymers as the OL-OlGfill polymers, such as the homopolymers and copolymers etc. containing, as the major constituent, ethylene, propylene, and the like and the acrylates and methacrylate polymers produced from monomers having the formula wherein R is a hydrogen or methyl radical and R is a hydrogen or an alkyl radical having from 1 to 6 carbon atoms, inclusive. Examples of monomers represented by Formula II include methyl acrylate, ethyl acrylate, npropyl acrylate, isopropyl acrylate, n-butyl acrylate, tbutyl acrylate, isobutyl acrylate, n-amyl acrylate, t-amyl acrylate, hexyl acrylate, and their corresponding alkyl methacrylates.

Additional examples of monomers which may be used to form the thermoplastic vinyl polymers encompassed by the present invention, polymerized either singularly or in combination with each other or with the other c0rn pounds set forth hereinabove, are such monomers as the unsaturated alcohol esters, more particularly, the allyl, methallyl, vinyl, methvinyl, butenyl, etc., unsaturated esters of aliphatic and aromatic monobasic acids such, for instance, as acetic, propionic, butyric, crotonic, succinic, glutaric, adipic, maleic, fumaric, itaconic, benzoic, phthalic, terephthalic, benzoylphthalic, etc., acids; the saturated monohydric alcohol esters, e.g., the methyl, ethyl, propyl, isopropyl, butyl, sec.-butyl, amyl, etc., esters of ethylenically unsaturated aliphatic monobasic acids, illustrative examples of which appear above; vinyl cyclic compounds (including monovinyl aromatic hydrocarbons), e.g., styrene, 0-, m-, and p-chlorostyrenes,

-flu-orostyrenes, -methylstyrenes, -ethylstyrenes, -cyanostyrenes, the various poly-substituted styrenes such, for example, as the various di-, tri-, and tetra-chlorostyrenes, -bromostyrenes, -fiuorostyrenes, -methylstyrenes, -ethylstyrenes, -cyanostyrenes, etc., vinyl pyridine, divinyl benzene, diallyl benzene, the various allyl cyanostyrenes, the various alpha-substituted styrenes and alpha-substituted ring-substituted styrenes, e.g., alphamethyl-styrene, alpha-methyl-para-methyl styrene, etc.; unsaturated ethers, e.g., ethyl vinyl ether, diallyl ether, etc.; unsaturated amides, for instance, N-allyl caprolactam, acrylamide, and N-substituted acrylamides, e.g., N- allyl acrylamide, N-methyl acrylamide, N-phenyl acrylamide, etc.; unsaturated ketones, e.g., methyl vinyl ketone, methyl allyl ketone, etc.; methylene malonic esters, e.g., methylene methyl malonate, etc.

Other examples of monomers that can be used as polymers to form the resin portion of our novel flameretardant compositions are the vinyl halides, more particularly, vinyl fluoride, vinyl chloride, vinyl bromide, and vinyl iodide, and the various vinylidene compounds,

including the vinylidene halides, e.g., vinylidene chloride, vinylidene bromide, vinylidene fluoride, and vinylidene iodide, other comonomers being added, if needed, in order to improve the compatibility and copolymerization characteristics of the mixed monomers.

More specific examples of allyl compounds that can be polymerized to useful polymers, useful in the production of our novel flame-retardant compositions, are allyl methacrylate, diallyl carbonate, allyl lactate, allyl trichloro silane, diallyl phthalate, diallyl methylgluconate, diallyl tartronate, diallyl tartrate, diallyl mesaconate, the diallyl ester of muconic acid, diallyl chlorophthalate, diallyl dichlorosilane, the diallyl ester of endomethylene tetrahydrophthalic anhydride, triallyl tricarballylate, triallyl cyanurate, triallyl citrate, triallyl phosphate, tetrallyl silane, tetrally-l silicate, hexaallyl disiloxane, allyl diglycol carbonate, etc. Other examples of allyl compounds that may be employed are given, for example, in US. Patent No. 2,510,503 issued June 6, 1950.

These above mentioned monomers may be polymerized, copolymerized, etc., in any known manner such as by free-radical generating catalysts, irradiation, anion and cation type catalysts and the like, said method of polymerization forming no part of the present invention.

The phosphinic acids As mentioned above, we have discovered that the addition of phosphinic acids to a thermoplastic resin results in the production of resinous compositions having excellent flame-retardant properties. According to the present invention, any phosphinic acid, stable to processing conditions, may be used for this purpose. A preferred group of phosphinic acids, however, are those represented by Formula I, above. The phosphinic acids may be incorporated into the resins in flame-retarding amounts, i.e., generally amounts ranging from about by weight, to about 35%, by weight, preferably to 25%, by weight,'based on the weight of the polymer, have been found sufiicient.

These phosphinic acids are generally known in the art and can be incorporated into the resin by any known method. That is to say, the flame-retardant phosphinic acid additive may be added to the resin by milling the resin and the acid on, for example, a two-roll mill, in a Banbury mixer etc., or the acid may be added by molding the acid and resin simultaneously, extruding the acid ano resin or by merely blending the resin in powder form with the acid and thereafter forming the final desired article, i.e. by casting. Additionally, the phosphinic acid may also be added during the resin manufacture, i.e., during the monomer polymerization procedure, provided the catalyst etc. and other ingredients of the polymerization system are inert to the phosphinic acid. For example, the acid may be added to the monomer or a combination of the monomer and polymer and the mixture cast to form the final article.

The phosphinic acids set forth hereinabove may be produced in any known manner without varying from the scope of the present invention. Various methods for the production of phosphinic acids of this type are disclosed in, for example, a book by Kosolapolf, Organophosphorus Compounds, John Wiley & Sons, New York, N.Y., publishers, pp. 129 et seq., 1950, which is hereby incorporated herein by reference.

Generally, the procedure for the production of these phosphinic acids comprises reacting an excess of a compound of the formula R-PH with hydrogen peroxide wherein R and R are as defined above in regard to Formula I, under the following conditions: hydrogen peroxide slowly is added to an appropriate solvent (such as methanol) containing a suitable secondary phosphine while maintaining a gentle reflux. Excess peroxide is decomposed by boiling the solution with a small amount of charcoal, which is then filtered, and the solvent evaporated. The phosphinic acid, if a solid, is recrystallized from an appropriate solvent and isolated by filtration. If the phosphinic acid is a liquid, it is purified by distillation. Yields usually are from 50% to of the theoretical, said procedures, however, forming no part of the present invention.

Examples of compounds which are represented by Formula I and are therefore useful in producing the novel compositions of the present invention include:

phenylphosphinic acid, tolylphosphinic acid, xylylphosphinic acid, naphthylphosphinic acid, methylphosphinic acid, ethylphosphinic acid, propylphosphinic acid, n-butylphosphinic acid, t-butylphosphinic acid, isobutylphosphinic acid, amylphosphinic acid, hexylphosphinic acid, cyclohexylphosphinic acid, heptylphosphinic acid, octylphosphinic acid, cyclopentylphosphinic acid, hydroxymethylphosphinic acid, 2-hydroxyethylphosphinic acid, Z-hydroxypropylphosphinic acid, 3-hydroxypropylphosphinic acid, 3-hydroxycyclopentylphosphinic acid, 4-hydroxybutylphosphinic acid, 2-hydroxybutylphosphinic acid, l-hydroxybutylphosphinic acid,

. 2-hydroxycyclopentylphosphinic acid,

S-hydroxypentylphosphinic acid, 3-hydroxypentylphosphinic acid, 6-hydroxyhexylphosphinic acid, 4-hydroxyhexylphosphinic acid, 2-hydroxycyclohexylphosphinic acid, l-hydroxyhexylphosphinic acid, 3-hydroxyheptylphosphinic acid, 2-hydroxyheptylphosphinic acid, 7-hydroxyheptylphosphinic acid, 5-hydroxyoctylphosphinic acid, 8-hydroxyoctylphosphinic acid, l-hydroxyoctylphosphinic acid, 3-hydroxyoctylphosphinic acid, cyanomethylphosphinic acid, 2-cyanoethylphosphinic acid, 3-cyanopropylphosphinic acid, l-cyanopropylphosphinic acid, Z-cyanobutylphosphinic acid, 4-cyanobutylphosphinic acid, S-cyanopentylphosphinic acid, 1-cyanopentylphosphinic acid, 3-cyanopentylphosphinic acid, 4-cyanohexylphosphinic acid, 6-cyanohexylphosphinic acid, Z-cyanohexylphosphinic acid, 7-cyanoheptylphosphinic acid, S-cyanoheptylphosphinic acid, Z-cyanoheptylphosphinic acid, S-cyanooctylphosphinic acid, S-cyanooctylphosphinic acid, l-cyanooctylphosphinic acid, 4-cyanooctylphosphinic acid, l-carboxy-1-hydroxymethylphosphinic acid, l-carboxy-l-hydroxyethylphosphinic acid, 2-carboxy-l-hydroxyethylphosphinic acid, 2-carboxy-2-hydroxyethylphosphinic acid, l-carboxy-l-hydroxypropylphosphinic acid, 3-carboxy-1-hydroxypropylphosphinic acid, 6-ca-rboxy-3 hydroxyhcxylphosphinic acid,

. 6-carboxy-6-hydroxyhexylphosphinic acid, 1-carboxy-S-hydroxyhexylphosphinic acid, 8-carboXy-8-hydroxyoctylphosphinic acid, 8-carboxy-l-hydroxyoctylphosphinic acid, 6-carboxy-8-hydroxyoctylphosphinic acid, carboxymethylphosphinic acid, l-carboxyethylphosphinic acid, Z-carboxyethylphosphinic acid, l-carboxypropylphosphinic acid, 2-carboxypropylphosphinic acid, 3-carboxypropylphosphinic acid, 4-carboxybutylphosphinic acid, l-carboxybutylphosphinic acid, 5-carboxypentylphosphinic acid, 3-carboxypentylphosphinic acid, 6-carboxyhexylphosphinic acid, 7-carboxyheptylphosphinic acid, 8-carboxyoctyiphosphinic acid, S-carboxyoctylphosphinic acid, 1-carboxyocty1phosphinie acid, diphenylphosphinic acid, ditolylphosphinic acid, diXylylphosphinic acid, dinaphthylphosphinic acid, dimethylphosphinic acid, diethylphosphinic acid, dipropylphosphinic acid, di-n-butylphosphinic acid, di-t-butylphosphinic acid, diisobutylphosphinic acid, diamylphosphinic acid, dihexylphosphinic acid, dicyclohexylphosphinic acid, diheptylphosphinic acid, dioctylphosphinic acid, dicyclopentylphosphonic acid, bis hydroxymethyl phosphinic acid, bis 2-hydroxyethyl phosphinic acid, bis Z-hydroxypropyl phosphinic acid, bis 3-hydroxypropyl phosphinic acid, bis 3-hydroxycyanopentyl phosphinic aci d, bis 4-hydroxybutyl) phosphinic acid, bis 2-hydroxybutyl phosphinic acid, bis( l-hydroxybutyl) phosphinic acid, bis(Z-hydroxycyclopentyl)phosphinic acid, bis S-hydroxypentyl phosphinic acid, bis 3 -hydroxypentyl phosphinic acid, bis 6-hydroxyhexyl phosphinic acid, bis(4-hydroxyhexyl)phosphinic acid, bis(2-hydroxycyclohexyl)phosphinic acid, bis l-hydroxyhexyl)phosphinic acid, bis(3-hydroxyheptyl)phosphinic acid, bis Z-hydroxyheptyl phosphinic acid, bis(7-l1ydroxyheptyl)phosphinic acid, bis S-hydroxyoctyl phosphinic acid, bis(S-hydroxyoctyl)phosphinic acid, bis l-hydroxyoctyl)phosphinic acid, bis (3 -hydroxyoctyl phosphinic acid, bis cyanomethyl phosphinic acid, bis(2-cyanoethyl)phosphinic acid, bis(3-cyanopropyl) phosphinic acid, bis l-cyanopropyl phosphinic acid, bis(Z-cyanobutyl) phosphinic acid, bis(4-cyanobutyl) phosphinic acid, bis S-cyanopentyl phosphinic acid, bis 1-cyanopentyl)phosphinic acid, bis 3 -cyan-opentyl phosphinic acid, bis(4-cyanohexyl) phosphinic acid, bis 6-cyanohexy1 phosphinic acid, bis 2-cyanohexyl phosphinic acid, bis(7-cyanoheptyl) phosphinic acid, bis S-cyanoheptyl phosphinic acid, bis Z-cyanoheptyl phosphinic acid, bis 8-cyanooctyl phosphinic acid, bis( 1-carboxy-1-hydroxyethyl) phosphinic acid,

6 bis Z-carboxy-l -hydroxyethyl phosphinic acid, bis Z-carboxy-Z-hydroxyethyl) phosphinic acid, bis( 1-carboxy-l-hydroxypropyl)phosphinic acid, bis 3-carboxy- 1 -hydroxypropyl) phosphinic acid, bis(6-carboxy-3-hydroxybexyl)phosphinic acid, bis 6-carboxy-6-hydroxyhexyl) phosphinic acid, bis( 1-carboxy-5-hydroxyhexyl phosphinic acid, bis 8-carboXy-8-hydroxyoctyl) phosphinic acid, bis( 8-carboXy-1-hydroxyoctyl)phosphinic acid, bis 6-carboxy-8-hydroxyoctyl phosphinic acid, bis carboxymethyl phosphinic acid, bis l-carboxyethyl)phosphinic acid, bis(Z-carboxyethyl) phosphinic acid, bis( 1-carboxypropyl)phosphinic acid, bis(2-carboxypropyl) phosphinic acid, bis (3-carboxypropy1) phosphinic acid, bis (4-carboxybutyl) phosphinic acid, bis( l-carboxybuty1)phosphinic acid, bis 5 -carb oxypentyl) phosphinic acid, bis( 3-ca-rboxypentyl) phosphinic acid, bis 6-carboxyhexyl phosphinic acid, bis 7-carboxyheptyl) phosphinic acid, bis(8-carb0xyoctyl) phosphinic acid, bis S-carboxyoctyl) phosphinic acid, bis l-carboxyoctyl phosphinic acid, 1-cyanocyclopentylphosphinic acid, 3-cyanocyclopentylphosphinic acid, 2-carboxycycl-opentylphosphinic acid, 4-carboxycyclohexylphosphinic acid, 3-cyanocyclohexylphosphinic acid, bis( l-cyano cyclopentyl phosphinic acid, bis 3-cyanocyclopentyl phosphinic acid, bis(2carboxycyclopentyl)phosphinic acid, bis(4-carb0Xycyclohexy1)phosphinic acid, bis 3-cyanocyclohexyl phosphinic acid, methylpropylphosphinic acid, phenyltolylphosphinic acid,

' hydroxymethylpropylphosphinic acid,

, 1-bydroxybutyl-2-hydroxycyclohexylphosphinic acid,

2-cyanoethylphenylphosphinic acid, 1-cyanocyclopentylmethylphosphinic acid, 1-carboxy-1-hydroxyethylnaphthylphosphinic acid, 3-hydroxybutyl-l-cyanoethylphosphinic acid, 1-carboxy-1-hyd-roxypropyltolylphosphinic acid, hexylisobutylphosphinic acid, 4-cyanobutylcyanomethylphosphinic acid, 2-hydroxyethyl-1-hydroxyethylphosphinic acid, methyl-3-hydroxybutylphosphinic acid, 2-carboxy-Z-hydroxyethylphenylphosphinic acid, cyclohexyl-l-cyanoethylphosphinic acid, (3-hydroxycyclopentyl) phenylphosphinic acid,

( l-cyanoethyl xylylphosphinic acid, ethyl-n-butylphosphinic acid, 3-hydroxyoctyl-2-cyanocyc1opentylphosphinic acid, 2-carboXy-1-hydroxyethyl-2-cyanoethylphosphinic acid,

- and the like.

It is within the scope of the present invention to incorporate suoh ingredients as plasticizers, dyes, pigments,

stabilizers, antioxidants, antistatic agents and the like to our novel compositions without detracting from the advantageous properties thereof.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Any appropriate flame retardance test may be used to determine the flame retardance properties of any specific compound. One test Which is reasonably eificient is that designated as a modified version of ASTM test D-635 56T. The specifications for this test are: a specimen, 5" in length, 0.5" in width and 0.045" in thickness, is marked at the 1" and 4" lengths and is then supported with its longitudinal axis horizontal and its transverse axis inclined at 45 to the horizontal. A Bunsen burner with a 1-" blue flame is placed under the free end of the strip and is adjusted so that the flame tip is just in contact with the strip. At the end of 30 seconds, the flame is removed and the specimen is allowed to burn. If the specimen does not continue to burn after the first ignition it is immediately recontacted with the burner for another 30 second period. If, after the two burnings, the strip is not burned to the 4" mark, the specimen is designated as self-exinguishing or flame-retardant.

EXAMPLE 1 Eighty parts of polyethylene and 20 parts of dicyclohexylphosphinic acid are milled together on a two roll mill at about 170 C. The resulting milled composition is molded into strips 5" in length, 0.5" in width and 0.45" in thickness and said strips are then subjected to an art recognized fiame-retardance test. The strips pass the test and are therefore designated as flame-retardant.

Following the procedure of Example 1, examples were carried out utilizing different flame retardant agents and various thermoplastic resin polymers. The results of these examples are set forth in Table I, below. In each instance the resultant plastic-phosphinic acid mixture passed the flame-retardance test and was designated as flame and fire retardant. In the table PE=polyethylene; PP=-polypropylene; PMMA=poly(methyl methacrylate); PA= poly(acrylie acid); AN=a-crylonitrile; ST=styrene and BD=butadiene.

TABLE I Example Polymer R R Percent 2 PMMA Q 1-1 25 3 PE 04H c4119 25 4 m 3 3 5 5 PMMA G 3 6 m --Q Q 7 PE OHCH2 OI'ICH2 25 OH OH I I 8 PMMA. /C-(? /C- l 25 HO CH3 HO CH3 9 PE NCCHzCHz NCCHzCHz 25 O\ O\ 10 PE /CCHz-CH2 CCH2-CH2 25 HO H0 OH OH 14 PA HaC- H 20 15 PMMA HaC- H 25 I CH l6 Mixture OfBD-AN H 25 (1075%)* and AN-ST (25-90%).

17 PP j Z 18 PP CH3 H 20 19 PE CqFh H 20 TABLE I-Oontinued Example Polymer R R Percent PMMA CsHn H 25 MMA/ST/AN,71/19/10 CH CH; 25 PP C2H5 20 PE CBH17- PE O8H11- so 2s PMMA H- 3o CNCH2 CNCH2 1U CN(CH )o H 25 CHgCHzfiJH-(CHzM- CH3 20 30 PMMA HOCH2 H 15 31 PA HO(CHz)4- 32 PE CH3(CH-z)zClH(CHz)4 H 30 O H as PA COHz- H3C 25 34 MixtureofBD-AN(10 C(CH2)1 C(CH2)3-- 25 75%)* and AN-S'l (25-90%). HO HO 35 PE C-CHz-CH C2115 25 36 PMMA C-CH2-(|IH- H 20 HO O H 37 PP CCH(CH2)0 NCOHZCHZ 25 38 PE H 30 so PMMA Q 10 40 Q Q 20 41 PE CH3 CNCH2 42 PE H3O C-OH2CH2 30 HO CH 43 PP HOCH2CH 25 TABLE I-Contlnued Example Polymer R R Percent 44 PE 02m H3C@ 2o 45 PMMA 30 *U.S. Patent No. 2,439,202.

We claim:

1. A flame-retardant composition consisting essentially of a thermoplastic material selected from the group consisting of a polymer, and blends of polymers produced from at least one vinyl monomer selected from the group consisting of (1) a butadiene, .(2) an acrylonitrile, (3) an a-olefin, (4) a styrene and (5) a compound having the formula R O R wherein R is selected from the group consisting of hydrogen and a methyl radical and R is selected from the group consisting of hydrogen and an alkyl radical of from 1 to 6 carbon atoms, inclusive, and from about 5% to about 35%, by Weight, based on the weight of said material, of a phosphinic acid having the formula 0 R-E-OH wherein R is selected from the group consisting of (a) an :aryl radical containing from 6-10 carbon atoms, (b) an alkyl radical containing from 1-8 carbon atoms, and (c) a substituted alkyl radical containing from =18 carbon atoms and being substituted with a member selected from the group consisting of (I) cyano, (II) hydroxy, (III) carboxy and (IV) carboxy and hydroxy and R is selected from the group consisting of (w) hydrogen, (x) said (a), (y) said (b), and (2) said (0).

2. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is a polymer of an u-olefin.

3. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is a polymer of a compound having the formula 0 onFp-o wherein R is selected from the group consisting of hydrogen and a methyl radical and R is selected from the group consisting of hydrogen and an alkyl radical having from 1 to 6 carbon atoms, inclusive.

4. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is poly(methyl methacrylate).

5. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is a mixture of (A) a butadiene-acrylonitrile copolymer and (B)an acrylonitrile-styrene copolymer, the amount of A and B ranging from about 1075% to 90-25%, respectively.

6. A flame retardant composition according to claim 1 wherein the thermoplastic polymer is polypropylene.

7. A flame retardant composition consisting essentially of polyethylene and from about 5% to about 35%, by Weight, based on the weight of said polyethylene of dicyclohexylphosphinic acid.

8. A flame retardant composition consisting essentially of polyethylene and from about 5% to about 35%, by Weight, based on the weight of said polyethylene of dipheny'lphosphinic acid.

9. A flame retardant composition consisting essentially of polyethylene and from about 5% to about 35%, by weight, based on the weight of said polyethylene of di-n-butylphosphinic acid.

10. A flame retardant composition consisting essentially of poly(methyl methacrylate) and from about 5% to about 35%, by weight, based on the weight of said poly(methyl methacrylate) of dicycloliexylphosphinic acid.

11. A flame retardant composition consisting essentially of poly(methyl methacrylate) and from about 5% to about 35%, by weight, based on the weight of said poly(methyl methacrylate) of bis(l-carboxy-l-hydroxyethyl) phosphinic acid.

12. A flame retardant composition consisting essentially of poly(methyl methacrylate) and from about 5% to about 35%, by weight, based on the weight of said poly(methyl methacrylate) of cyclopentyl-l-hydroxycyclopentylphosphinic acid.

References Cited UNITED STATES PATENTS 2,230,371 2/ 1941 Bolton 26045 .7 2,370,903 3/1945 Hirschmann 260-50O 2,516,980 8/1950 Gray et al. 260-45.7 2,773,046 12/1956 Dunn et al. 26045.7 2,953,595 '9/1960 Rauhut et al. 252-8.1 2,997,454 8/1961 Leistner et al 26045.75 3,014,954 12/1961 Birum 260461 3,065,183 1 1/1962 Temin 252-78 3,078,248 2/1963 Ben 26030.6 3,249,562 3/1966 Schoepfle et al. 260-2.5

FOREIGN PATENTS 243,465 1/ 1961 Australia.

519,738 11/ 1953 Belgium.

526,531 -6/1965 Canada. 1,044,813 Ill 1958 Germany.

866,042 4/ 1961 Great Britain.

OTHER REFERENCES Modern Plastics Encyclopedia, vol. 40, No. 1A, Sep- 5 tember 1962, page 479 relied on.

Chemical Abstracts I, Subject Index, vol. 58, June 30, 1963, page 16628.

Chemical Abstracts II, Subject Index, vol. 57, December 31, 1962, page 1863S.

DONALD E. CZAIA, Primary Examiner.

LEON J. BERCOVITZ, F. MCKELVEY,

Assistant Examiners. 

1. A FLAME-RETARDANT COMPOSITION CONSISTING ESSENTIALLY OF A THERMOPLASTIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF A POLYMER, AND BLENDS OF POLYMERS PRODUCED FORM AT LEAST ONE VINYL MONOMER SELECTED FROM THE GROUP CONSISTING OF (1) A BUTADIENE, (2) AN ACRYLONITRILE, (3) AN A-OLEFIN, (4) A STYRENE AND (5) A COMPOUND HAVING THE FORMULA 